In general, brushless DC motors (also known as electronically commutated motors) include a multi-pole permanent magnet rotor, a multi-pole wound stator and commutation circuitry for selectively activating the stator phase windings to produce motor torque of a desired direction. Since correct activation and commutation of the stator phase windings requires that the orientation of the rotor magnet relative to the stator poles be known, the commutation circuitry must include one or more commutation sensors. Most commonly, commutation sensing is achieved with an array of Hall Effect sensors responsive to magnetic field domains produced by the rotor magnet. See, for example, the U.S. Pat. No. 4,934,041 to Hoover et al. and the U.S. Pat. No. 6,097,129 to Furtwängler et al., which disclose fixturing arrangements for positioning Hall Effect sensors in close proximity to the rotor magnet.
The rotor magnet field domains can be more reliably sensed by embedding Hall Effect sensors in the stator as described herein in respect to the prior art rotary actuator of FIG. 1. However, it is desired to avoid manufacturing costs associated with discrete Hall Effect sensors and interconnection of embedded Hall Effect sensors with the rest of the commutation circuitry. Accordingly, what is needed is an improved commutation sensing apparatus that is both reliable and cost-effective.